A recent UK study found that 28% of autistic children were diagnosed with autism after starting secondary school, a stage where self-concept and social identity are the main developmental tasks. This study uses Foucauldian Discourse Analysis to explore the discourses ten girls with a diagnosis of autism use in their constructions of self-concept and social identity in interviews and written journals. The actions that are made possible through the discourses employed are considered. Three discourses which participants draw upon are: a diagnostic discourse; an individualistic discourse; and a normativity discourse. These discourses were used to construct the self as a "legitimised autistic", as "a person with support needs", as "uniquely individual", as a person "in the process of becoming" and as a "self in hiding from a hostile world". Social identities based around constructs of "fitting in" and "sticking out" were identified. Implications for practice are suggested.